US1979919A - Machine for rolling screw threads - Google Patents

Description

1934- G. H. WAYNE MACHINE FOR ROLLING SCREW THREADS 2 Sheets-Sheet 1 Filed Jan. 13, 1933 l VENTOR Al.

ATTO R N EYS 9 l 9 7 w I 2 Sheets-Sheet 2 Filed Jan. 15, 1933 Nev. 6, 1934.

' V INVENTOR 6 0 )1. C Q ?Y W ATToRNEYs j atented Nov MACE FOR RQG SCREW Glenn H. Wayne, Waterbury,

Scovill Manufacturing ilompany,

Conn, assignor to Waterbury,

Conn, a corporation of Qonnecticut Application January 13, 1933, Serial No. 651,476

6 Claims.

This invention relates to machines for rolling screw threads.

In a patent granted January 27, 1925, No. 1,524,327, I have disclosed a machine for rolling g, screw threads in which one of the dies is capable of a limited compensating movement for the purpose of avoiding inaccuracies known as drunk threads.

It is an object of the present invention to provide an improved thread=rolling machine along the general lines of the machine of said patent, capable of attaining a. high degree of thread accuracy, particularly in the case of the smaller sizes of screws, and one that makes possible longer life for the dies.

With these general objects in View, the inven= tion consists in the features, combinations, details of construction and arrangements of parts which will first be described in connection with the accompanying drawings and then more particularly pointed out.

In the drawings:

Figure 1 is a plan view, with parts in section, of a thread-rolling machine constructed in accordance with the invention;

Figure 2 is an end View of the same;

Figure 3 is a sectional view (enlarged) taken longitudinally of one of the die units;

Figure i is a transverse sectional view of the same; and

Figures 5, 6 and '7 are exaggerated explanatory views of dies and blanks.

Referring to the drawings, there are provided two complementary dies for rolling threads on a blank which rolls between the dies as the thread is formed. The blank may be rolled between the dies by relative movement of the dies which may conveniently be flat blocks, one block being reciprocated with respect to'the other. As here shown as an example, slidable in upper and lower tracks 11, 12 of a bed block 13 is a slide 14 having a die-carrying portion 15. Mounted in the latter is a die block lfi-secured in place by means of clamps 17 and bolts 18. Secured to the slide 14 is the end of a pitman 20 driven from a disk 21 by a crank pin 22 mounted therein. Disk 21 is rotatably connected with a gear 23 meshing with a pinion 24 on a drive shaft 25. This shaft is rotated by a pulley 26 to which power may be applied in any suitable manner. As the drive shaft rotates, the slide 14 is moved back and forth to give an endwise reciprocation of die block 16.,

Opposite the reciprocating die is a complementary die 2'7. This latter, as hereinafter described, is mounted to have slight compensating movements but, as distinguished from die 16, the complementary die 2'7 is stationary, i. e. nonreciprocating.

As is more fully described in said Patent 1,524,327, the pposing faces of the two dies are so formed with a series of parallel die teeth 29 run ning lengthwise of the blocks but at an angle to the longitudinal axis thereof. The teeth of one die are opposed to the intervening grooves of the other (Fig. 5) and the dies are so spaced apart as that when a cylindrical blank is rolled between them a thread is formed on the blank.

Upon advance movement of the'reciprocating die 16, the blank is rolled between the two dies. 'Jjhat is, the blank revolves on its own axis and my travels along between the dies. For a half turn of the blank, the teeth of die 16 form thread portions in half the surface of the blank and the teeth of die 27 form thread portions in the other half of the blank. That is, referring to Fig. 7, 75 which represents a section through the blank, die 16, for example, has formed thread portions from the point X around to point Y and die 27, during the same half turn of the blank, has

. formed thread portions from Y around to X. m

During the next half turn of the blank the half threads formed by die 16 are presented to die 27 and the half threads formed by die 2'? are presented to die 16 for further formation or finishing or both. Ordinarily}, the complete thread is roughly formed during the first half turn or first few half turns, the remainder of the action being in the nature of a finishing or planishing operation.

Under ideal conditions the blank should start its axial rotation and traveling movement at the same instant and these movements should continue regularly and at the rate for which the dies are designed. It often happens, however, that the start of the axial rotationof the blank and its traveling movement are not simultaneous, or the rate of movement is irregular, or both. In other words, (there is a slippage of the blank with respect to the dies. As a result of this slippage, lacking compensatory provisions, the lead of the formed thread varies from the theoretical lead because that half of the thread formed by one die is out of true position when it moves around to the-other die and, consequently, the teeth of the latter cause the thread to be distorted, i. e. cause drunk threads.

Fig. 5 shows, diagrammatically and in an exaggerated manner, the ideal conditions. A represents half of the blank and B represents. one die.-

A. represents the same half of the blank after a 1 2 1,979,919 half turn and C represents the other die. As line or pivotal movement to compensate therefor.

5 shows, the thread formed by die B is, after the half turn, in true registry or mesh with the teeth of die 0.

Fig. 6 illustrates similarly the result of slippage of the blank if no compensation is provided for. At the right, the broken lines represent the teeth and grooves of the .die and the full lines represent the relative position of the thread on the blank after a half turn. As shown, the thread is not in proper registry or mesh with die C and consequently die 0 will distort the thread.

To overcome this defective action, it has been proposed to give one die a pivotal mounting, as disclosed in said Patent 1,524,327. The construction there disclosed has been satisfactory for the larger sizes of screws but somewhat less so for the smaller sizes. The construction of the present invention results in uniformly accurate threads for all sizes.

The presentinvention in its entirety includes a full floating die. That is, the die is mounted to be capable of right line movements in its own plane and of swinging movements on any one of an indeterminate number of pivots perpendicular to the face of the die. This may be conveniently accomplished by suspending the die between opposing sets of springs.

In the embodiment here illustrated as an example, die 27 is secured on a ledge 31 of a die carrier 32 by means of clamps 33 and bolts 34 so that die I and carrier may be considered as one. Carried by a bed block 35 is a support 36 having an upstanding flange 37 and adjustably secured in position by bolts 38. Mounted on the support 36 are two brackets 39 and the die carrier floats between these brackets and the flange 37.

To this end, as here shown as an example, the carrier is bifurcated to straddle fiange37 (Fig. 4) Seated in pockets 40 in the flange are coil springs 41, the upper ends of which take into pockets'42 in the die carrier, whereby the die carrier is sus-- pended on the two springs.

The top of the die carrier 32 is engaged by two headed pins 43 projecting from hollow bosses 44 on brackets 39. Confined in these bosses 44 betweenthe heads of pins 43 and plug nuts 45 are coiled springs 46. Guide pins, in the form of bolts 47, are carried by the support and extend through holes 48 on the die carrier, these holes being enough larger than the bolts to permit tilting movements of the carrier.

Thus the die carrier with-its die floats between the two sets of springs. It can move up or down with a right line movement and canswing on any of an indeterminate number of theoretical pivots perpendicular to the face of the die. That is,-the die is full-floating as distinguished from the die disclosed in'said Patent 1,524,327 which can swing onlyfrom a single fixed pivot.

The die carrier here shown as an example is also capable of a slight compensating movement on theoretical pivots parallel to the face of the die. This is accomplished by providing a slight clearance between flange 37 of the support and the bifurcated portion of the carrier. This movement compensates for inequalities in the blanks. That is, if any portion of the blank is slightly oversize the die 27 can yield either by a right dies being mounted What may be termed the initial position of the die can be set by adjusting the compression or springs 46 by means of plug nuts 45, lock nuts '49 serving to hold the parts in adjusted position.

With the construction of the present invention,

either end of-the die can move up or down and can do so at any time during the thread-rolling stroke. As a result, not onlyare drunk threads avoided but strain on the die teeth, due-to inaccurate mesh with the thread being formed, is

a die unit suspended between the two sets of springs, a complementary die, and means for causing relative movement between said dies to roll a blank between the same.

2. In an apparatus for rolling screw threads,

and in combination, a support, two sets of oppositely disposed springs carried by said support, a die unit suspended between the twov sets of springs, means for adjusting the compression of at least one of said sets of springs to set the initial position of the die unit, a complementary die, and means for causing relative movement between said dies to roll a blank between the same.

3.; In an apparatus for rolling screw threads, and in combination, a support having an upstanding flange, a plurality of springs seated in pockets in said flange and projecting above the latter, a die unit straddling said flange and suspended on said springs, a complementary die, and means for causing relative movement between said dies to roll a blank between the same. 4. In an apparatus for rolling screw threads, and in combination, two complementary dies, means for causing relativemovement between the dies to roll a blank between the same, one of said to be capable of compensating movements about an indeterminate number of theoretical pivots perpendicular to the face of the die.

5. In an apparatus for rolling screw threads,

and in combination, a support, a plurality of springs carried by said support, a die unit suspended on said springs to be capable of compensating movement about an indeterminate number of theoretical pivots perpendicular to the face of the die, a complementary die, and means for causing relative movement of said dies to roll a blank between the same.

6. In an apparatus for rolling screw threads, and in combinatij", a support, a plurality of springs carried by 's'aid support, a die unit suspended on said springs to be capable of compensating movement about an indeterminate number of theoretical pivots perpendicular to the face of the die, guide pins carried by said support and passing through holes in said die unit, said holes being sufficiently oversize to permit tilting movements of the die unit, a complementary die, and means for causing relative movement of said dies to roll a blank between the same.

GLENN H. WAYNE.

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